1. Field of the Invention
The present invention pertains to silver recovery devices for silver laden solutions; more particularly to a silver recovery device used to recover silver obtained during photographic processes; and still more particularly to an improved silver recovery cell therefor.
2. Description of the Prior Art
It is well known that silver based compounds are a major constituent of photographic film. After the film has been exposed to light, it is subjected to a "developer" solution. The light exposure combined with a bath in the developer solution results in some of the silver in the silver compounds being converted to metallic silver, resulting in an image of the film. In order to prevent any remaining silver compounds from being affected by further exposure to light, the film is chemically processed by a "fixer" solution to remove the remaining silver compounds that were not affected by the aforesaid light exposure. This "fixes" the film and allows it to be subsequently viewed in lighted environments without the image thereon being affected. This developing process of photographic film is very well known in the art and results in large amounts of silver being released into the fixer solution. For both environmental and economic reasons, it is very desirable to recover as much of this released silver as is possible.
It is known in the prior art to recover silver from photographic solutions by use of an electrical silver plating system. An example of such a system is described in U.S. Pat. No. 3,875,032 to Thompson, where a power supply is electrically connected to an anode and cathode, each being immersed in a photographic fixer solution. When electricity is applied to the electrodes, silver, present in the solution as either suspended metallic silver or as suspended or dissolved silver compounds, is caused to plate on the cathode. In Thompson, the photographic fixer solution is contained in a tank rendering the process awkward and inefficient.
An improved type of electrical silver plating system is described in U.S. Pat. No. 4,612,102 to Brimo et al. Brimo et al teach that the silver plating process may be performed utilizing a cell having a cylindrically shaped canister for containing the photographic fixer solution. Brimo et al teach that a rod shaped anode of graphite material is connected to a removable top and that a cylindrically shaped cathode having a longitudinal slit encircles the anode and is resident in the canister. Terminals connect a power supply to the cathode and the anode. While this cell is an improvement over the tank of Thompson, it suffers from inability to visually inspect the status of the silver plating that is occurring on the cathode, a factor that is critical in controlling quality of the operation. Further, because the anode is connected to the top, silver tends to plate mainly adjacent to the top, where the fixer solution is entering the canister, rather than along the entire longitudinal length of the cathode, resulting in inefficient operation.
Accordingly, what is needed is a silver recovery device which incorporates a cell having the structural features of visual inspection of silver plating at the cathode and uniform plating of the cathode surface.